I have a blank user control (child) and during Page_Load i create some text boxes and a button. I also add an event to the button.
I then load that user control dynamically from a placeholder in another usercontrol (parent).
Both controls are rendered correctly but when i click on the button, the event isnt fired.
Any ideas on how to handle the event?
Child code:
protected void Page_Load(object sender, EventArgs e)
{
/*... other user controls ..*/
UpdateButton = new LinkButton();
UpdateButton.ID = "buttonid";
UpdateButton.Text = "text";
UpdateButton.Click += new EventHandler(UpdateButton_Click);
this.Controls.Add(UpdateButton);
}
protected override void Render(HtmlTextWriter writer)
{
for (int i = 0; i < this.Controls.Count; i++)
{
this.Controls[i].RenderControl(writer);
}
}
public void UpdateButton_Click(object sender, EventArgs e)
{
//Do stuff
}
Parent code:
protected void Page_Load(object sender, EventArgs e)
{
placeholder.Controls.Clear();
ChildControl uc = (ChildControl)LoadControl("~/UserControls/ChildControl.ascx");
placeholder.Controls.Add(uc);
}
If i use the child control directy (ie without the parent the control) the click event is raised and handled nicely. But when i use the parent control, the debugger wont even hit a breakpoint inside UpdateButton_Click().
Thanks in advance.
I think I know what might be happening. In your parent Page_Load you are calling placeholder.Controls.Clear(); This does what you would imagine and clears the control, including any events that have occurred. What happens when remove this line? Do you get an additional one created on each postback?
Related
I have a DropDownList and a CheckBox on my web form. After the DropDownList is clicked and this event is posted back to the server. DropDownList_SelectedIndexChanged event is called on the server side. Inside that event handler, I have CheckBox.Checked = true, But I couldn't make the page on the client side to reflect this change (CheckBox.Checked = true). How do I achieve this? Or am I in the wrong direction to use the DropDownList's event handler to update the CheckBox because the page firstly reloads and then DropDownList_SelectedIndexChanged is called?
Page load method:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
this.DropDownList1.Items.Clear();
AddItemsToDropDownList();
}
}
DropDownList selected index changed event handler:
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
var selected = this.DropDownList1.SelectedItem.Text;
CheckBox checkBox = GetCheckBoxToBeSetByText(selected);
checkBox.Checked = true;
}
OK. Found the issue. Actually there is nothing wrong with the code in my original post. But to make a smallest sample when I posted, I removed some "extra" code. The below is the "complete" code (OK, fine, I still removed some code). As you can see, I put the CheckBox into a static Dictionary. Each time the SelectedIndexChanged event handler is called, it's modifying the CheckBox in that static Dictionary, which means it's modifying the CheckBox object created from the last session? (still not clear here) Looks like each time when a postback message is received, a new set of CheckBox objects are created. Bear with me if this is known to everybody here already because I only have two days of experience on this web development thing up to today.
private static Dictionary<Environment, CheckBox> EnvironmentsCheckBoxes;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
EnvironmentsCheckBoxes = new Dictionary<Environment,CheckBox>();
EnvironmentsCheckBoxes.Add(Environment.Dev1, this.Dev1_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.Dev2, this.Dev2_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.QA, this.QA_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.QA2, this.QA2_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.Demo, this.Demo_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.Prod, this.Prod_CheckBox);
EnvironmentsCheckBoxes.Add(Environment.UAT, this.UAT_CheckBox);
}
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
var selected = this.DropDownList1.SelectedItem.Text;
if (selected == "Dev1")
{
EnvironmentsCheckBoxes[Environment.Dev1].Checked = true;
}
else if (selected == "Dev2")
{
...
}
...
}
I am dynamically creating link buttons on user control using a place holder and the eventhandler attached to the link button click+=new Event(Button_Click) is not firing
Thanks in Advance
Code Snippet of
protected override void OnInit(EventArgs e)
MenuListPlaceHolder.Controls.Add(new LiteralControl("<li>"));
ctrl.ID = this.UniqueID + (nCounter++).ToString();
ctrl.Text = cardType.Name;
ctrl.Click += new EventHandler(this.CardName_Click);
MenuListPlaceHolder.Controls.Add(ctrl);
MenuListPlaceHolder.Controls.Add(new LiteralControl("</li>"));
When clicked post back event is fired but not executing CardName_Click
You have to attach it on Page_Load event
like so:
protected void Page_Load(object sender, EventArgs e) {
this.Btn.OnClick+=new Event(Button_Click)
}
you should check it: here to learn about page cycle
I have created a User Control(Popupcontrol) and in that control i have created a property(PageType) and when i am using the Popupcontrol on the page then i set the property(pagetype) according to the page.
but now there is some problem i have to two button on the page and on the second button click i want to change the pagetype property .So is there any solution for the same.
Based on your comment, it seems you bind the data (PageType property in your question) in the Page_Load event, instead of this it should be done in overrided DataBind method which should be called if the page is not in post back request (otherwise your data will be overwritting in the next Page_Load event as you mentioned in your comments):
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
{
DataBind();
}
}
public override void DataBind()
{
PageType = someValue;
}
after this your click handler may looks like:
protected void button2_Clicked(object sender, EventArgs e)
{
PageType = someOtherValue;
}
Are you setting the variable in a page load event? You may need to add:
if (!Page.IsPostback) {
// Code here.
}
I have an htmlgeneric control and on run time i am adding control in it but when i click on any button then added controls disappear.
Dynamically created controls need to be created on every post back. You also need to give them an ID if you want to maintain and restore their ViewState.
For example, this will show the TextBox the first time the page is loaded, but on any subsiquent page loads, the control will be missing:
protected void Page_Init(object sender, EventArgs e)
{
if (!IsPostBack)
{
TextBox newControl = new TextBox()
{
ID = "newControl"
};
SomeControl.Controls.Add(newControl);
}
}
However, if you create the control on every postback with the same Id, then the control will be maintained with it's Text:
protected void Page_Init(object sender, EventArgs e)
{
TextBox newControl = new TextBox()
{
ID = "newControl"
};
SomeControl.Controls.Add(newControl);
}
Here's a good article about dealing with dynamic controls.
I have some code which involves dynamically creating new buttons, when a user clicks on a particular button. However the EventHandlers defined for these dynamically created buttons do not execute when I click on any one of them. Here is the errant code snippet:
protected void Page_Load(object sender, EventArgs e)
{
.......
btn1.Click += new EventHandler(this.btn1_Click);
.......
}
protected void btn1_Click(object sender, EventArgs e)
{
.......
LinkButton btn2 = new LinkButton();
btn2.Click += new EventHandler(this.btn2_Click);
.........
}
protected void btn2_Click(object sender, EventArgs e)
{
.......
}
The code execution never enters btn2_Click(). Am I doing something wrong here?
Try declare LinkButton btn2 as global variable and and wire the event btn2.Click += new EventHandler(this.btn2_Click) as the controls are created.
btn2 disappears as soon as you leave the btn1 event handler. It's a local variable, and goes away as soon as it's out of scope.
Did you ever see the second button? Did you click on it? If so, then you clicked on the wrong button. This one you added never appeared on your page.
In order for a control to become visible (and to render into HTML), it must be placed inside of the Controls collection of a visible control. You're not doing anything with it.